- Clean up the __rb_map_vma() logic
The logic of __rb_map_vma() has a error check with WARN_ON() that makes
sure that the index does not go past the end of the array of buffers. The
test in the loop pretty much guarantees that it will never happen, but
since the relation of the variables used is a little complex, the
WARN_ON() check was added. It was noticed that the array was dereferenced
before this check and if the logic does break and for some reason the
logic goes past the array, there will be an out of bounds access here.
Move the access to after the WARN_ON().
- Consolidate how the ring buffer is determined to be empty
Currently there's two ways that are used to determine if the ring buffer
is empty. One relies on the status of the commit and reader pages and what
was read, and the other is on what was written vs what was read. By using
the number of entries (written) method, it can be used for reading events
that are out of the kernel's control (what pKVM will use). Move to this
method to make it easier to implement a pKVM ring buffer that the kernel
can read.
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Merge tag 'trace-ringbuffer-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull trace ring-buffer updates from Steven Rostedt:
- Clean up the __rb_map_vma() logic
The logic of __rb_map_vma() has a error check with WARN_ON() that
makes sure that the index does not go past the end of the array of
buffers. The test in the loop pretty much guarantees that it will
never happen, but since the relation of the variables used is a
little complex, the WARN_ON() check was added. It was noticed that
the array was dereferenced before this check and if the logic does
break and for some reason the logic goes past the array, there will
be an out of bounds access here. Move the access to after the
WARN_ON().
- Consolidate how the ring buffer is determined to be empty
Currently there's two ways that are used to determine if the ring
buffer is empty. One relies on the status of the commit and reader
pages and what was read, and the other is on what was written vs what
was read. By using the number of entries (written) method, it can be
used for reading events that are out of the kernel's control (what
pKVM will use). Move to this method to make it easier to implement a
pKVM ring buffer that the kernel can read.
* tag 'trace-ringbuffer-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
ring-buffer: Make reading page consistent with the code logic
ring-buffer: Check for empty ring-buffer with rb_num_of_entries()
0074adea39